Study on the New Oscillating Reactions in theCu（Me₆［14］4,11-dieneN₄）²⁺-Pyruvic acid-NaBrO₃-H₂SO₄ System

In this paper new oscillating chemical reactions with the participation of pyruvic acid, an important intermediate in the glycolysis,as organic substrate and hexamethyl-tetraazamacrocycliccopper（II） complex as catalyst in acidic bromate media are reported. Here the macrocyc licligand is 5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene.The typical oscillation curve is shown in Fig.1.The colour of the solution changes periodically because of the oxidation-reduction［CuL］²⁺（orange）\underset+_\mathrme\stackrel-\mathrme\rightleftharpoons［CuL］³⁺ （yellow）.The concentration oscillations of this system are damped rapidly due to the consumption of the catalyst.We also got the domain of the existence of oscillations in the coordinates of NaBrO 3 and pyruvic acid concentrations （Fig.2） fixing the initial concentrations of ［CuL］₂₊ and H₂SO₄ as 1.6×10^-3 and 1.0mol/L respectively.The effects of the initial concentration of pyruvic acid, ［CuL］²⁺, H₂SO₄ and NaBrO₃ on the oscillation period（t_p）,the induction time（t_in）,the amplitude of oscillation （A） and the oscillation times （I） are shown in Fig. 3～Fig. 6 respectively.
Increasing reaction temperature will shorten the oscillation life, oscillation periods and induction time. The effects of reaction temperature on the oscillation periods are illustrated in Fig.7. The apparent activation energy of the oscillations is 53.21kJ/mol. We also studied the effects of Ag⁺,Hg²⁺, CCl₄,V_c,glucose,acetonitrile,acrylamide and H₂O₂ on the oscillations. The mechanism of the oscillations is also discussed briefly. The pyruvic acid is brominated and oxidized in the oscillations as well as malonic acid.